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Mybatis-plus Quickstart

Mybatis-plus quickstart guide.

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By 51348761z
25 min read
Mybatis-plus Quickstart

This is a quickstart guide for Mybatis-plus, a powerful enhancement to MyBatis that simplifies CRUD operations and provides additional features.

1. Add Dependency

Add the following dependency to your pom.xml if you’re using Maven:

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<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.10</version>
</dependency>

2. Configure Data Source

Configure your data source in application.properties or application.yml:

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spring:
  datasource:
    url: jdbc:mysql://localhost:3306/your_database
    username: your_username
    password: your_password
    driver-class-name: com.mysql.cj.jdbc.Driver
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl # Enable SQL logging

3. Quick Start

3.1 Create data table

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create table user (
  id bigint auto_increment not null comment 'Primary Key',
  name varchar(50) character set utf8mb4 collate utf8mb4_general_ci default null comment 'User Name',
  age int default null comment 'User Age',
  email varchar(50) character set utf8mb4 collate utf8mb4_general_ci default null comment 'User Email',
  version bigint not null default '0' comment 'Version Number for Optimistic Locking',
  create_time datetime not null default current_timestamp comment 'Creation Time',
  update_time datetime not null default current_timestamp on update current_timestamp comment 'Update Time',
  primary key (id)
) engine=InnoDB default charset=utf8mb4 collate=utf8mb4_general_ci comment='User Table';

Table Creation Notes

  • character set 指定字符编码（如 utf8mb4 支持完整 Unicode），确保存储与读取一致。
  • collate 指定排序与比较规则（如 utf8mb4_general_ci 为不区分大小写的通用排序）。
  • TIMESTAMP、DATETIME 通常映射到 java.time.LocalDateTime（旧版本可用 java.sql.Timestamp）。
  • CURRENT_TIMESTAMP 等标识符（含 NOW()、LOCALTIME、LOCALTIMESTAMP）可用于 DEFAULT 或 ON UPDATE 获取当前时间。
    • CURRENT_TIMESTAMP：MySQL 标准，支持 DEFAULT 和 ON UPDATE。
    • NOW()：MySQL 专用，等同于 CURRENT_TIMESTAMP，但不支持 ON UPDATE。
    • LOCALTIME 和 LOCALTIMESTAMP：SQL 标准，等同于 CURRENT_TIMESTAMP，但不支持 ON UPDATE。
    • ON UPDATE 只能用于 TIMESTAMP 和 DATETIME 列。
  • DEFAULT CURRENT_TIMESTAMP 插入时自动赋值，ON UPDATE CURRENT_TIMESTAMP 更新行时刷新；可组合使用。
  • ENGINE=InnoDB 指定存储引擎，常见选项还有 MyISAM、MEMORY、CSV、ARCHIVE、BLACKHOLE 及插件引擎。
    • InnoDB：支持事务、行级锁，适合高并发读写。
    • MyISAM：不支持事务，适合读多写少的场景。
    • MEMORY：数据存储在内存中，适合临时数据处理。
    • CSV：以 CSV 格式存储数据，适合数据交换。
    • ARCHIVE：适合存储大量历史数据，压缩存储。
    • BLACKHOLE：数据写入后丢弃，适合日志收集。

3.2 Create Entity Class

com.wongs.mybatisplusdemo.entity.User

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package com.wongs.mybatisplusdemo.entity;

import com.baomidou.mybatisplus.annotation.*;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.time.LocalDateTime;
import java.time.LocalTime;

@Data
@TableName(value = "user")
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class User {

    @TableId(type = IdType.AUTO)
    private Long id;

    private String name;

    private Integer age;

    private String email;

    @TableField(value = "create_time", fill = FieldFill.INSERT)
    private LocalDateTime createTime;

    @TableField(value = "update_time", fill = FieldFill.INSERT_UPDATE)
    private LocalDateTime updateTime;

    @Version
    private Long version;

}

Entity Class Annotation Summary

  • @TableName("user"): maps the entity to the user table.
  • @TableId(type = IdType.AUTO): marks id as the primary key using auto-increment strategy.
  • @TableField(value = "create_time", fill = FieldFill.INSERT): binds createTime to create_time and auto-fills on insert.
  • @TableField(value = "update_time", fill = FieldFill.INSERT_UPDATE): maps updateTime to update_time and auto-fills on insert/update.
  • @Version: enables optimistic locking via the version column.

IdType.AUTO：使用数据库自增 ID 作为主键。
IdType.NONE：无特定生成策略，如果全局配置中有 IdType 相关的配置，则会跟随全局配置。 IdType.INPUT：在插入数据前，由用户自行设置主键值。 IdType.ASSIGN_ID：自动分配 ID，适用于 Long、Integer、String 类型的主键。默认使用雪花算法通过 IdentifierGenerator 的 nextId 实现。 IdType.ASSIGN_UUID：自动分配 UUID，适用于 String 类型的主键。默认使用 UUID 生成器通过 IdentifierGenerator 的 nextUUID 实现。

3.3 Create Mapper Interface

com.wongs.mybatisplusdemo.mapper.UserMapper

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package com.wongs.mybatisplusdemo.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.wongs.mybatisplusdemo.entity.User;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface UserMapper extends BaseMapper<User> {
  // No additional methods needed; BaseMapper provides CRUD operations
}

Mapper Interface Summary

BaseMapper 是 Mybatis-Plus 提供的一个通用 Mapper 接口，它封装了一系列常用的数据库操作方法，包括增、删、改、查等。通过继承 BaseMapper，开发者可以快速地对数据库进行操作，而无需编写繁琐的 SQL 语句。

  • extends BaseMapper<User>: inherits CRUD methods for User entity.
  • @Mapper: marks the interface as a MyBatis mapper for component scanning.
  • No need for XML mapper files; MyBatis-plus generates SQL based on method names and entity mappings.

3.4 Add @MapperScan to main application class

com.wongs.mybatisplusdemo.MybatisPlusDemoApplication

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package com.wongs.mybatisplusdemo;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.wongs.mybatisplusdemo.mapper")
public class MybatisPlusDemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(MybatisPlusDemoApplication.class, args);
    }

}

@MapperScan Summary

  • @MapperScan("com.wongs.mybatisplusdemo.mapper"): specifies the package to scan for mapper interfaces, enabling MyBatis to find and register them.

4. Common Usage Examples

4.1 CRUD Operations

MyBatis-plus provides built-in methods for common CRUD operations including insert (create), selectById (read), updateById (update), and deleteById (delete), etc.

Create

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@Test
void testInsert() {
    User user = User.builder()
        .name("John Doe")
        .age(30)
        .email("john.doe@example.com")
        .build();
    userMapper.insert(user);
}

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-- SQL settings for create_time and update_time
alter table user modify column create_time datetime default current_timestamp comment 'Creation Time';
alter table user modify column update_time datetime default current_timestamp on update current_timestamp comment 'Update Time';

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JDBC Connection [HikariProxyConnection@168702939 wrapping com.mysql.cj.jdbc.ConnectionImpl@5d9d8e46] will not be managed by Spring
==>  Preparing: INSERT INTO user ( name, age, email, create_time, update_time ) VALUES ( ?, ?, ?, ?, ? )
==> Parameters: robot(String), 20(Integer), xxx@abc.com(String), null, null
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@779228dc]

当数据库允许传入 null 字段，并且 createTime、updateTime 未赋值时，MyBatis-plus 会写入 null，数据库默认值不会生效，这与我们的预期不符。

方案 1：仅在有值时写入列
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public class User {
    // ...other fields...

    @TableField(value = "create_time", insertStrategy = FieldStrategy.NOT_NULL)
    private LocalDateTime createTime;

    @TableField(value = "update_time", fill = FieldFill.INSERT_UPDATE)
    private LocalDateTime updateTime;
    // ...other fields...
}

通过 insertStrategy = FieldStrategy.NOT_NULL，空值时跳过该列，保留数据库默认值（启用该策略后不要再设置 fill，因为 fill 会使得 insertStrategy 的配置被忽略，即断言该字段必有值）。

方案 2：数据库强制非空并手动赋值
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alter table user modify column create_time datetime not null default current_timestamp comment 'Creation Time';
alter table user modify column update_time datetime not null default current_timestamp on update current_timestamp comment 'Update Time';

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@Test
void testInsert() {
    LocalDateTime now = LocalDateTime.now();
    User user = User.builder()
        .name("John Doe")
        .age(30)
        .email("john.doe@example.com")
        .createTime(now)
        .updateTime(now)
        .build();
    userMapper.insert(user);
}

对列加非空约束并在代码中显式赋值，可确保时间戳始终符合业务要求。

Read

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@Test
void testRead() {
    User user = userMapper.selectById(5L);
    System.out.println(user);
}

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JDBC Connection [HikariProxyConnection@1535684464 wrapping com.mysql.cj.jdbc.ConnectionImpl@546083d6] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email,create_time,update_time,version FROM user WHERE id=?
==> Parameters: 5(Long)
<==    Columns: id, name, age, email, create_time, update_time, version
<==        Row: 5, Eve, 50, eve@example.com, 2025-09-28 05:05:23, 2025-09-28 07:13:20, 0
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@68f776ee]
User(id=5, name=Eve, age=50, email=eve@example.com, createTime=2025-09-28T05:05:23, updateTime=2025-09-28T07:13:20, version=0)

Update

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@Test
void testUpdate(){
    // method 1, 根据实体entity和条件构造器wrapper进行更新
    User user = User.builder()
            .age(52)
            .updateTime(LocalDateTime.now())
            .build();
    UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();
    updateWrapper.eq("id", 1L);
    userMapper.update(user, updateWrapper);

    // method 2
    // 根据入参entity的id（主键）进行更新，对于entity中非空的属性，会出现在UPDATE语句的SET后面，即entity中非空的属性，会被更新到数据库中。
    User user1 = User.builder()
            .id(1L)
            .age(30)
            .updateTime(LocalDateTime.now())
            .build();
    userMapper.updateById(user1);
}

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JDBC Connection [HikariProxyConnection@170132562 wrapping com.mysql.cj.jdbc.ConnectionImpl@6807989e] will not be managed by Spring
==>  Preparing: UPDATE user SET age=?, update_time=? WHERE (id = ?)
==> Parameters: 52(Integer), 2025-09-28T07:31:20.648017(LocalDateTime), 1(Long)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7e50eeb9]
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7a274521] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@799306600 wrapping com.mysql.cj.jdbc.ConnectionImpl@6807989e] will not be managed by Spring
==>  Preparing: UPDATE user SET age=?, update_time=? WHERE id=?
==> Parameters: 30(Integer), 2025-09-28T07:31:20.857118(LocalDateTime), 1(Long)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7a274521]

Delete

BaseMapper 一共提供了如下几个用于删除的方法

  • deleteById 根据主键 id 进行删除
  • deleteBatchIds 根据主键 id 进行批量删除
  • deleteByMap 根据 Map 进行删除（Map 中的 key 为列名，value 为值，根据列和值进行等值匹配）
  • delete(Wrapper wrapper) 根据条件构造器 Wrapper 进行删除
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@Test
void testDelete() {
    userMapper.deleteById(50L);
}

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JDBC Connection [HikariProxyConnection@288398804 wrapping com.mysql.cj.jdbc.ConnectionImpl@18ac4af6] will not be managed by Spring
==>  Preparing: DELETE FROM user WHERE id=?
==> Parameters: 50(Long)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7a3643e3]

4.2 Wrapper - 条件构造器

MyBatis-Plus 提供了一套强大的条件构造器（Wrapper），用于构建复杂的数据库查询条件。Wrapper 类允许开发者以链式调用的方式构造查询条件，无需编写繁琐的 SQL 语句，从而提高开发效率并减少 SQL 注入的风险。

SQL注入是一种攻击手法，攻击者通过在输入中插入恶意SQL语句来操控数据库查询。若应用直接拼接未校验的输入，攻击者可绕过认证、窃取或篡改数据。使用参数化查询和输入校验可有效防范。

在 MyBatis-Plus 中，Wrapper 类是构建查询和更新条件的核心工具。以下是主要的 Wrapper 类及其功能：

  • AbstractWrapper：这是一个抽象基类，提供了所有 Wrapper 类共有的方法和属性。它定义了条件构造的基本逻辑，包括字段（column）、值（value）、操作符（condition）等。所有的 QueryWrapper、UpdateWrapper、LambdaQueryWrapper 和 LambdaUpdateWrapper 都继承自 AbstractWrapper。

  • QueryWrapper：专门用于构造查询条件，支持基本的等于、不等于、大于、小于等各种常见操作。它允许你以链式调用的方式添加多个查询条件，并且可以组合使用 and 和 or 逻辑。

  • UpdateWrapper：用于构造更新条件，可以在更新数据时指定条件。与 QueryWrapper 类似，它也支持链式调用和逻辑组合。使用 UpdateWrapper 可以在不创建实体对象的情况下，直接设置更新字段和条件。

  • LambdaQueryWrapper：这是一个基于 Lambda 表达式的查询条件构造器，它通过 Lambda 表达式来引用实体类的属性，从而避免了硬编码字段名。这种方式提高了代码的可读性和可维护性，尤其是在字段名可能发生变化的情况下。

  • LambdaUpdateWrapper：类似于 LambdaQueryWrapper，LambdaUpdateWrapper 是基于 Lambda 表达式的更新条件构造器。它允许你使用 Lambda 表达式来指定更新字段和条件，同样避免了硬编码字段名的问题。

AbstractWrapper 中用于构建SQL语句中的 WHERE 条件的方法进行部分列举:

  • eq：equals，等于
  • allEq：all equals，全等于
  • ne：not equals，不等于 !=
  • gt：greater than ，大于 >
  • ge：greater than or equals，大于等于 ≥
  • lt：less than，小于 <
  • le：less than or equals，小于等于 ≤
  • between：相当于SQL中的 BETWEEN
  • notBetween
  • like：模糊匹配。like("name","黄")，相当于SQL的 name like '%黄%'
  • likeRight：模糊匹配右半边。likeRight("name","黄")，相当于SQL的 name like '黄%'
  • likeLeft：模糊匹配左半边。likeLeft("name","黄")，相当于SQL的 name like '%黄'
  • notLike：notLike("name","黄")，相当于SQL的 name not like '%黄%'
  • isNull：isNull("name")，相当于SQL的 name is null
  • isNotNull：isNotNull("name")，相当于SQL的 name is not null
  • in：in("id", 1, 2, 3)，相当于SQL的 id in (1, 2, 3)
  • and：SQL连接符 AND
  • or：SQL连接符 OR
  • apply：用于拼接SQL，该方法可用于数据库函数，并可以动态传参

Conditional Query Example

(1) QueryWrapper and UpdateWrapper
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@Test
void testQueryAndUpdateWrapper(){
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    // conditional query
    queryWrapper.gt("age", 50);
    List<User> userList = userMapper.selectList(queryWrapper);

    // conditional update
    UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();
    updateWrapper.eq("name", "David").set("age", 18);
    userMapper.update(updateWrapper);

}

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JDBC Connection [HikariProxyConnection@753027610 wrapping com.mysql.cj.jdbc.ConnectionImpl@46ee7013] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email,create_time,update_time,version FROM user WHERE (age > ?)
==> Parameters: 50(Integer)
<==    Columns: id, name, age, email, create_time, update_time, version
<==        Row: 68, Nancy, 55, nancy@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 69, Oscar, 60, oscar@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 78, Xavier, 52, xavier@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 86, Felix, 53, felix@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 90, Jack, 58, jack@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 94, Nick, 51, nick@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 99, Sara, 54, sara@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==      Total: 7
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7858d31d]
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@22ff11ef] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1613378103 wrapping com.mysql.cj.jdbc.ConnectionImpl@46ee7013] will not be managed by Spring
==>  Preparing: UPDATE user SET age=? WHERE (name = ?)
==> Parameters: 18(Integer), David(String)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@22ff11ef]
(2) Condition

条件构造器的诸多方法中，均可以指定一个boolean类型的参数condition，用来决定该条件是否加入最后生成的WHERE语句中，比如:

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@Test
void testCondition(){
    String name = "m";
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.like(StringUtils.hasText(name), "name", name);
    List<User> users = userMapper.selectList(queryWrapper);
    // equivalent to
    if (StringUtils.hasText(name)) {
        queryWrapper.like("name", name);
        List<User> users2 = userMapper.selectList(queryWrapper);
    }
}

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JDBC Connection [HikariProxyConnection@753027610 wrapping com.mysql.cj.jdbc.ConnectionImpl@46ee7013] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email,create_time,update_time,version FROM user WHERE (name LIKE ?)
==> Parameters: %m%(String)
<==    Columns: id, name, age, email, create_time, update_time, version
<==        Row: 67, Mike, 29, mike@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 81, Amy, 32, amy@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 85, Emily, 36, emily@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 93, Mary, 33, mary@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 100, Tom, 30, tom@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==      Total: 5
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@53ba7997]
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5e055ce1] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@846778469 wrapping com.mysql.cj.jdbc.ConnectionImpl@46ee7013] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email,create_time,update_time,version FROM user WHERE (name LIKE ? AND name LIKE ?)
==> Parameters: %m%(String), %m%(String)
<==    Columns: id, name, age, email, create_time, update_time, version
<==        Row: 67, Mike, 29, mike@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 81, Amy, 32, amy@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 85, Emily, 36, emily@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 93, Mary, 33, mary@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 100, Tom, 30, tom@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==      Total: 5
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5e055ce1]
(3) Entity as Condition

调用构造函数创建一个Wrapper对象时，可以传入一个实体对象。后续使用这个Wrapper时，会以实体对象中的非空属性，构建WHERE条件（默认构建等值匹配的WHERE条件，这个行为可以通过实体类里各个字段上的@TableField注解中的condition属性进行改变）。

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@Test
void textEntityAsCondition(){
    User user = User.builder()
            .name("Tom")
            .build();
    QueryWrapper<User> userQueryWrapper = new QueryWrapper<>(user);
    List<User> users = userMapper.selectList(userQueryWrapper);
}

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JDBC Connection [HikariProxyConnection@1875372072 wrapping com.mysql.cj.jdbc.ConnectionImpl@49925d21] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email,create_time,update_time,version FROM user WHERE name=?
==> Parameters: Tom(String)
<==    Columns: id, name, age, email, create_time, update_time, version
<==        Row: 100, Tom, 30, tom@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@338d47b]
(4) LambdaWrapper

lambda条件构造器，支持lambda表达式，可以不必像普通条件构造器一样，以字符串形式指定列名，它可以直接以实体类的方法引用来指定列。

像普通的条件构造器，列名是用字符串的形式指定，无法在编译期进行列名合法性的检查，这就不如lambda条件构造器来的优雅。

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@Test
void testLambdaQuery(){
    LambdaQueryWrapper<User> lambdaQueryWrapper = new LambdaQueryWrapper<>();
    lambdaQueryWrapper.like(User::getName, "T").lt(User::getAge, 50);
    List<User> users = userMapper.selectList(lambdaQueryWrapper);
}

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JDBC Connection [HikariProxyConnection@1186076210 wrapping com.mysql.cj.jdbc.ConnectionImpl@7404aff2] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email,create_time,update_time,version FROM user WHERE (name LIKE ? AND age < ?)
==> Parameters: %T%(String), 50(Integer)
<==    Columns: id, name, age, email, create_time, update_time, version
<==        Row: 71, Quentin, 30, quentin@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 73, Steve, 42, steve@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 74, Tina, 26, tina@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 76, Victor, 37, victor@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 83, Cathy, 24, cathy@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 91, Kate, 22, kate@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 100, Tom, 30, tom@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==      Total: 7
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@dae5e0]
(5) Custom SQL

  • Annotation

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    @Select("select * from user)
List<User> selectAllUsers();

  • XML Mapper

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    <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.wongs.mybatisplusdemo.mappers.UserMapper">
  <select id="selectRaw" resultType="com.wongs.mybatisplusdemo.po.User">
        SELECT * FROM user
    </select>
</mapper>


public interface UserMapper extends BaseMapper<User> {
  List<User> selectRaw();
}
(6) Pagination

MyBatis-Plus 提供了内置的分页功能，简化了分页查询的实现。

分页是将大量数据分割成多个页面进行显示的技术，常用于Web应用中以提升用户体验和性能。通过分页，用户可以逐页浏览数据，而不是一次性加载所有数据，从而减少加载时间和服务器压力。

配置分页插件，在 ‘MybatisPlusConfig’ 类中添加分页插件配置。

MyBatis-Plus 的分页插件 PaginationInnerInterceptor 提供了强大的分页功能，支持多种数据库，使得分页查询变得简单高效。
于 v3.5.9 起，PaginationInnerInterceptor 已分离出来。如需使用，则需单独引入 mybatis-plus-jsqlparser 依赖. 具体配置请参考 MyBatis-Plus 官方文档。

com.wongs.mybatisplusdemo.config.MybatisPlusConfig

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@Configuration
public class MyBatisPlusConfig {

    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor (){
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL)); // 如果配置多个插件, 切记分页最后添加
        // 如果有多数据源可以不配具体类型, 否则都建议配上具体的 DbType
        return interceptor;
    }
}

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@Test
void testPagination() {
    LambdaQueryWrapper<User> lambdaQueryWrapper = new LambdaQueryWrapper<>();
    lambdaQueryWrapper.between(User::getAge, 20, 50);

    Page<User> page = new Page<>(3, 2); // query page 3, 2 records per page
    Page<User> userPage = userMapper.selectPage(page, lambdaQueryWrapper); // execute pagination query
    System.out.println("Total records: " + userPage.getTotal());
    System.out.println("Total pages: " + userPage.getPages());
    System.out.println("Current page records: " + userPage.getCurrent());
    List<User> records = userPage.getRecords(); // Get current page records
    records.forEach(System.out::println);
}

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JDBC Connection [HikariProxyConnection@1359003971 wrapping com.mysql.cj.jdbc.ConnectionImpl@7a021f49] will not be managed by Spring
==>  Preparing: SELECT COUNT(*) AS total FROM user WHERE (age BETWEEN ? AND ?)
==> Parameters: 20(Integer), 50(Integer)
<==    Columns: total
<==        Row: 42
<==      Total: 1
==>  Preparing: SELECT id,name,age,email,create_time,update_time,version FROM user WHERE (age BETWEEN ? AND ?) LIMIT ?,?
==> Parameters: 20(Integer), 50(Integer), 4(Long), 2(Long)
<==    Columns: id, name, age, email, create_time, update_time, version
<==        Row: 60, Frank, 50, frank@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==        Row: 62, Heidi, 27, heidi@example.com, 2025-09-28 08:58:40, 2025-09-28 08:58:40, 0
<==      Total: 2
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@225e09f0]
Total records: 42
Total pages: 21
Current page records: 3
User(id=60, name=Frank, age=50, email=frank@example.com, createTime=2025-09-28T08:58:40, updateTime=2025-09-28T08:58:40, version=0)
User(id=62, name=Heidi, age=27, email=heidi@example.com, createTime=2025-09-28T08:58:40, updateTime=2025-09-28T08:58:40, version=0)
(7) Code Generator

MyBatis Plus 提供了代码生成器，可以根据数据库表自动生成实体类、Mapper 接口、Service 类和 Controller 类。 MyBatis-Plus 代码生成器配置官方文档参考

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FastAutoGenerator.create("url", "username", "password")
        .globalConfig(builder -> builder
                .author("Baomidou")
                .outputDir(Paths.get(System.getProperty("user.dir")) + "/src/main/java")
                .commentDate("yyyy-MM-dd")
        )
        .packageConfig(builder -> builder
                .parent("com.baomidou.mybatisplus")
                .entity("entity")
                .mapper("mapper")
                .service("service")
                .serviceImpl("service.impl")
                .xml("mapper.xml")
        )
        .strategyConfig(builder -> builder
                .entityBuilder()
                .enableLombok()
        )
        .templateEngine(new FreemarkerTemplateEngine())
        .execute();

4.3 Optimistic Locking

乐观锁是一种并发控制机制，用于确保在更新记录时，该记录未被其他事务修改。 MyBatis-Plus 提供了 OptimisticLockerInnerInterceptor 插件，使得在应用中实现乐观锁变得简单。

乐观锁的实现原理
乐观锁的实现通常包括以下步骤：

  • 读取记录时，获取当前的版本号（version）。
  • 在更新记录时，将这个版本号一同传递。
  • 执行更新操作时，设置 version = newVersion 的条件为 version == oldVersion。
  • 如果版本号不匹配，则更新失败。

Step 1: Add Optimistic Locker Interceptor

在 MybatisPlusConfig 类中添加乐观锁插件配置。

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@Configuration
public class MyBatisPlusConfig {

    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor (){
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new OptimisticLockerInnerInterceptor());
        return interceptor;
    }
}

Step 2: Add @Version Annotation to Entity Class

在实体类中，使用 @Version 注解标记版本字段。

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@Data
@TableName(value = "user")
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class User {

    // ...other fields...

    @Version
    private Integer version;

}

Then, you can use the updateById method to perform an update with optimistic locking.

Java, Mybatis-plus
java mybatis-plus mysql
This post is licensed under CC BY 4.0 by the author.